Hiromi Oka (岡 大海, Oka Hiromi, born July 15, 1991 in Kurashiki, Okayama, Japan) is a professional Japanese baseball player. He plays outfielder for the Chiba Lotte Marines. Oka is known as person that he has the same name as heroine of Aim for the Ace!, Japanese animation. Oka is outfielder but he had worn No. 18, it is known as uniform number that great pitcher wear in Japanese professional baseball, from 2017 to 2018.